Prepaid wireless service (e.g., cellular service) is a form of wireless service in which a user must pay in advance for use of the wireless service. Typically, a user purchases from a prepaid wireless service provider a definite amount of usage of a wireless network (e.g., number of airtime minutes, amount of data transfer, number of messages) at an initially pre-defined exchange of monetary value versus units of usage. These measures of units of usage have commonly been valued as minutes of usage of the wireless network in the case of airtime minutes. When the user places or receives a call from their wireless device or otherwise uses the service, the user's pre-purchased airtime minutes or other appropriate units of usage are deducted from the user's account. The rate at which pre-purchased units of usage are deducted per unit of usage is known as the deduct rate. Once the pre-purchased units of usage have been exhausted, the user is denied service until the user purchases additional units or the user's account parameters are otherwise replenished.
Certain prepaid wireless devices possess internal accounting capabilities that allow for real-time call debiting of account parameters that are solely maintained within the wireless device, where such wireless devices include an internal memory which stores the deduct rate and a billing algorithm that monitors usage of the wireless device and debits the internally stored account parameters accordingly. In this manner, all accounting operations associated with use of the wireless device are performed within the wireless device itself, as opposed to traditional cell phone billing platforms in which accounts are managed, tracked and billed by components on the network side of the wireless network. Performing all accounting operations on the wireless device itself minimizes the communication traffic required between the wireless service provider's host processer that handles billing operations and the wireless device or other network components, thus reducing network traffic and congestion and expanding the overall traffic handling capacity of the wireless network.
Once prepaid units of usage have been exhausted on a prepaid wireless device possessing internal accounting capabilities, the wireless device becomes inoperable for such usage until the user's internal account is replenished with additional units of usage. This has traditionally required individualized replenishment messages to be generated and transmitted to each specific prepaid wireless device in order for a wireless service provider to replenish prepaid units of usage or to update the deduct rate or other account parameters.
Prepaid wireless devices having internal accounting capabilities and account and subscription parameters maintained solely within the wireless device can be especially useful for a Mobile Virtual Network Operator (MVNO), which is an operator that buys bulk airtime from Mobile Network Operators (MNO's) and provides subscription services to customers. A MNO is an operator that owns the network infrastructure, airwaves, and provides airtime to subscribers, or sells bulk airtime to other entities. A MVNO does not generally own any network infrastructure or airwaves.
Instead, in order to provide subscription services, MVNO's tend to incorporate a loosely coupled subscription model, wherein they rely on infrastructure outside the domain of the MNO's to provide various subscription parameters. A loosely coupled subscription model is a system wherein the wireless device (i.e., handset or subscriber unit) does not have a provisioning model based off the network infrastructure of the MNO (e.g., the switch).
A MVNO based loosely coupled model for provisioning handset parameters utilizing a MNO network is illustrated in FIG. 1. The MVNO configuration 10 could deploy one or more MVNO secure message generating servers (PSMS) 14 that rely on information provided by the MVNO provisioning server or control server 12. Should a wireless device 24 be always powered on and registered to the MNO network, the MVNO message generating server 14 sends a formatted Short Message Service (SMS) message to the wireless device 24 via a base transceiver station (BTS) or cell site 20, and the wireless device 24 replies with an acknowledgement, thereby completing a transaction. The formatted SMS message is routed via a Short Message Service Center (SMSC) 16, residing in the MNO broadcast region 22, and the SMSC 16 delivers the message to the wireless device 24, should it be notified by a Home Location Register (HLR) 18 indicating that the wireless device 24 is registered to the network. The wireless device 24, upon receipt of the SMS message and replenishment of its subscription parameters, sends a reply back to the MVNO provisioning server 12, thereby completing a transaction.
The complexity of this server-initiated replenishment operation is illustrated in FIG. 2 that illustrates an end to end sequence diagram for a server-initiated replenishment model for a MVNO. During a replenishment cycle, the MVNO provisioning server 12 computes the replenishment value for every wireless device 24 (if there are groups of wireless devices 24 to be replenished, then this computation must be performed for each wireless device). The MVNO provisioning server 12 then sends the calculated replenishment to the MVNO message generating server 14, which generates an SMS message and sends it to the SMSC 16. The SMSC 16 checks with the HLR 18 to determine whether the wireless device 24 has registered to the network and is powered on. If so, the SMS message is forwarded to the wireless device 24, which replenishes its parameters based on contents of the SMS message. The wireless device 24 then sends an acknowledgement back to the MVNO provisioning server 12, thereby completing the process
This operation involves a pseudosynchronous operation that requires the wireless device 24 to be powered on most of the time in order to receive the replenishment message, and recovers should the wireless device 24 have power cut during the operation or other temporary system backlogs. However, there are times when a wireless device 24 can be switched off for extended periods of time, and may not be used for days, weeks or even months. This model of handset usage does not lend itself to a model where a thorough two-way synchronization between the back-end MVNO provisioning server 12 and the wireless device 24 can take place when the wireless device 24 has been turned off. If a wireless device 24 is switched off for a long duration of time, the replenishment message could time out at the SMSC 16 or the MVNO provisioning server 12 could time out, such that the desired replenishment does not occur. Compounding this problem, if multiple wireless devices 24 are turned off, the network elements (e.g., MVNO provisioning server 12, SMSC 16) can become backlogged with messages, causing a vast amount of messages either to become expired on the back-end of the MVNO (e.g., MVNO provisioning servers 12) or the back-end of the MNO's (e.g., SMSC's 16), respectively, leading to the subscriber not having a timely allocation of airtime or other usage replenished on their wireless device 24.
Even when wireless devices 24 are powered on, another problem with this server-initiated replenishment approach is that it can cause network elements to become backlogged when a large number of wireless devices 24 have their account parameters replenished on a periodic basis (e.g., monthly), such that a replenishment message is sent to each wireless device 24 at the beginning of period. For example, if a wireless service provider needed to replenish account parameters or update account settings for a large number of wireless devices 24 at the same time (e.g., 500,000 users), this would require 500,000 individual messages to be generated and transmitted to each of the 500,000 wireless devices 24. These large numbers of individualized messages provide a tremendous burden on the service provider to create the individual messages and also create severe congestion on the network elements (e.g., MVNO provisioning server 12, SMSC 16, etc.) and the wireless network itself to deliver such a large number of individual messages at substantially the same time at the beginning of a replenishment period.